1. Field of the Invention
The present invention generally relates to a ZigBee network. More particularly, the present invention relates to a method to transmit a multicast data packet to a multicast group consisting of some nodes among nodes forming a ZigBee network.
2. Description of the Related Art
ZigBee Alliance is an association of companies working together to enable cost-effective, low-power, and wireless network products based on IEEE 802.15.4 standard.
Unicast routing protocol of a ZigBee network includes a cluster tree protocol and an Ad hoc On Demand Distance Vector (AODV) protocol. Typically, the ZigBee network supports the unicast routing protocol, but not a multicast routing protocol. However, the concept of the multicast is a noticeable method to effectively support sensor networks in the ZigBee network.
FIG. 1 illustrates a general ZigBee network consisting of a plurality of nodes. Referring now to FIG. 1, descriptions are made on a delivery of a data packet in the ZigBee network consisting of the plurality of the nodes. The ZigBee network consists of nodes A to M. The node A is a ZigBee coordinator (ZC) for managing the nodes forming the ZigBee network. Nodes B to M transmit and receive a data packet under the control of the node A.
The reason for requiring the multicast routing protocol is explained below. It is assumed that the node A transmits the same data packet to the nodes C, E, G, H and I. In this situation, the node A can unicast or multicast the data packet. In detail, the node A unicasts a data packet in which an address of the node C is set to a destination address. In addition, the node A unicasts a data packet in which an address of the node E is set to a destination address. In such a way, the node A unicasts the data packets in sequence, to thus transmit the same data packet (with different destination addresses) to the nodes C, E, G, H and I.
Alternatively, the node A may broadcast the data packet to nodes forming a ZC. In this situation, the node A sets a destination address of the data packet to an address indicating a broadcast packet. Accordingly, the nodes B to M receive the data packet from the node A. However, the nodes B, D, F, and J to M do not need the received data packet, and thus drop the data packet.
As explained above, there is a disadvantage that the packet is not delivered to all of the nodes forming the ZigBee network. That is, in case of unicasting a packet, the transmitting nodes have to transmit packets with different destination addresses several times. Furthermore, overhead increases since undesired nodes receive a broadcast packet.